Vanessa Trump “went gangster” on Aubrey O’Day when she found out about the ­reality star’s affair with her husband, Donald Trump Jr., we’re told.

Don Jr. infamously had a lengthy affair with O’Day in 2011 after she appeared as a contestant on NBC’s “The Apprentice,” on which he served as an “adviser” to his father, Donald Trump. Don Jr. even considered leaving Vanessa for O’Day, until his dad told him to “knock it off.”

But when Vanessa — who at the time had recently given birth to their third child — discovered the infidelity, she called singer O’Day to blast her with both barrels.

“Vanessa went gangster,” said a source with knowledge of the call. “Aubrey was shocked. Vanessa said some extremely unladylike things to her.”

We’re told that the call involved the usually demure Vanessa comparing her and childless O’Day’s bodies and sexual capabilities in violently graphic terms. Apparently, this is a side of the glossy blonde she occasionally ­unleashes at extreme moments.

Vanessa made a notable appearance in a 1998 New York Magazine article about Leonardo DiCaprio’s “p—y posse” after it was claimed she had hooked up with the actor in a nightclub. But that wasn’t the wild part.

In the piece, a former classmate of then-Vanessa Haydon called her a “total gangster bitch.” “She was an ill thug,” the classmate said. “She went out with this Latin King for like three years,” the classmate added, referring to the notorious Hispanic street gang. Hinting at her dramatic tendencies, classmates had also voted Vanessa “Most likely to appear on ‘Ricki Lake.’ ”

Other sources told Page Six that before she met and began dating Don Jr. in 2003, Vanessa was regularly seen at Rikers to visit a jailed man they described as her “Latin kingpin paramour.”

As Page Six first reported, Vanessa filed for divorce from Don Jr. after 12 years of marriage in March. They have five kids.